The present invention relates generally to polyamides, and more particularly to novel polyamides which exhibit intumescent flame retardant properties, to a process for preparing the polyamides, and to flame retardant coating formulations of the intumescent type containing the novel polyamides.
The importance of protecting building materials and other heat and fire-vulnerable substrates against the effects of high temperatures and flames is widely recognized. The use of flame retardant coating formulations to impart flame retardance to these substrates has been known for several years. A class of these flame retardant coating formulations is formulations of the intumescent type.
Intumescence is a state of being tumid or inflated. An intumescent coating is one that will enlarge or expand to form a cellular structure when exposed to sufficient heat. Coatings of the intumescent type provide protection to heat and/or fire-vulnerable substrates by forming a flame retardant, thermally insulating barrier over the substrate.
The flame retardant coating formulations generally employed in the art are multicomponent materials containing an inorganic flame retardant component, (such as a phosphorus containing compound), a suitable film-forming binder, a dispersing agent, fillers and pigments, and an intumescent component. The intumescent component generally contains two ingredients: (1) a nonresinous chemical material, called a carbonific, which forms a large volume of carbonaceous char, and (2) a chemical material, sometimes referred to as a spumific, which upon thermal decomposition releases large quantities of nonflammable gaseous products. Typical flame retardant formulations of the above type are taught in U.S. Pat. Nos. 3,396,129; 3,440,201; 3,449,161; and 3,562,197.
U.S. Pat. No. 3,297,754 discloses a process for preparing polyamides from .alpha.,.alpha.-disubstituted .beta.-halopropionic acid amides by way of .beta.-lactams. The polymerization proceeds by a ring opening mechanism and consequently results in polyamide compositions differing in structure from the presently claimed compositions. Moreover, there is no teaching that the polyamides produced by the process of U.S. Pat. No. 3,297,754 exhibit intumescent flame retardant properties.